Pricing by sq ft is not the recommended way… instead figure how many 1 man days it will take to complete, multiply by how much you want to charge per day, add cost of materials and equipment, add 5% for overhead costs… BINGO!
Assuming measurements off of prints; Measure all surfaces and get the sq/ft total. You will need to know what type of finishes are specified. Go to your local paint store, with the measurements and prints in hand, talk to your sales rep. Your rep will know the current going prices to charge. If this price is too low bump it up to meet your needs.
Also while measuring, think about time and material costs. As mentioned, this is the best way to get at a price that you can work with.